Effect on South American CL: This proposal would elevate a taxon to species
rank that we currently treat as a subspecies.

Background: Kšnig et al. (1996) proposed, based on differences in
voice, size, and molecular data, that the southern Andean and Patagonian magellanicus
be elevated to species status from the widespread virginianus. Marks et
al. (1999) and others followed this treatment without any additional insight,
i.e., they repeated what was in Kšnig et al. (1996). However, Schulenberg et
al. (2007) followed traditional treatment (Traylor 1958) of magellanicus,
because of purported intergradation and individuals giving vocalizations of
both forms in northern Peru.

Analysis: Magellanicus is very similar in plumage to other virginianus
taxa, except for having shorter ear tufts and apparently being smaller in
size (mass, wing, tail, bill; Traylor 1958). However, as the always-thorough
Mel Traylor noted, the northern Andean magellanicus population (central
Peru, Bolivia) apparently is larger than southern populations (he noted that
this may be an altitudinal effect) and overlaps in size with nigrescens of
northern Peru, Ecuador, and Colombia. If North American populations are any
indication on the relevance of morphology, then plumage pattern and size have
little bearing on species limits. For example, within North America the eastern
nominate subspecies is boldly marked and richly colored, whereas birds in the
drier western portions of North America are relatively pale with less distinct
markings. These two subspecies freely interbreed where they come together in
the western Great Plains. Some individuals of northern wapacuthu are so
white with black barring that they resemble immature Bubo scandiaca!
Finally, darkest populations are found at the opposite sides of the continent.
Although not as extreme, morphological variation is considerable among
described forms in Central and South America. Therefore, plumage differences
have little to no merit in defining species limits within this group.

As
one would predict, the primary vocalization is likely the key in species
recognition, and although plumage variation is considerable within North
American populations, there is very little vocal differentiation. In contrast,
the song of birds referable to magellanicus in the central and southern
Andes and Patagonia is quite distinct from that of birds north of the Mara–—n
Valley in Peru and birds in the eastern lowlands of South America north of
northern Argentina. The song of magellanicus consists of two deep
hoots with emphasis on the second note, followed by a low guttural purring:
"bu-h—ohworrrr", whereas the typical song of virginianus consists
of two or more notes and lacks the ending purr (Kšnig et al. 1999, pers. obs.,
see Xeno-canto and Macaulay Library of Natural Sounds, Cornell Laboratory of
Ornithology [MLNS] websites).

Kšnig
et al. (1999) stated that magellanicus and the subspecies of virginianus
(nacurutu) found locally east of the Andes, are at least parapatric in
northwestern Argentina (depto. Salta): "where the lowlands and foothills
are occupied by B. v.nacurutu while in the rocky
"quebradas" and above timberline (3,000-4,000 m) B. magellanicus
is found." To my knowledge, there is no published information on the
potential contact of these two taxa elsewhere in Argentina. The recently
published Birds of Peru (Schulenberg et al. 2007) offered insight into
contact between magellanicus and nigrescens (Andes of Colombia,
Ecuador and northern Peru), stating that magellanicus may intergrade
with nigrescens in northern Peru. Recordings by the late Ted Parker from
Piura, Peru (MLNS 21879-80, 21890; listen to these on the MLNS website) appear
to indicate birds giving both call types.

Kšnig
et al. (1996) compared 960 base pairs of mitochondrial cyt-b sequence
data of virginianus with magellanicus and found that they differ
in nucleotide substitution by 1.6 %. However, there is no indication of sample size
(presumably one of each!) or locality data for the samples. Thus, it is unclear
what population of virginianus was compared with magellanicus. In
other words, data presented in that paper are meaningless without accompanying
pertinent information.

Recommendation: Although there may be more than one species within the virginianus
complex, to date, data are minimal and undocumented. What is needed is a
thorough vocal and genetic analysis of the entire group, especially in key
areas in northern Peru and northern Argentina (southeastern Bolivia?), before
we change the current treatment.Hence, I recommend a
"no" vote.

Comments from Remsen: "NO, for all the reasons stated by Mark.
I would also add that from Mark's description of the Kšnig et al. analysis, it
does not fit the definition of "science" because one could not
replicate it."

Comments from Stiles: "NO. Again, I agree with Mark that the
evidence currently available does not justify recognition of magellanicus as
a species - particularly as the molecular data are suspect and, as Van notes unrepeatable."

Comments from Stotz: "NO. I think that there are way too many
questions still about the relationship between magellanicus and virginianus.
I await better data on voice and genetics before going for this split."

Comments from Zimmer: "NO. As Mark correctly points out, the
morphological distinctions between magellanicus and the rest of the
virginianus group are not as great as the variation within the rest
of virginianus. Clearly, there is something going on vocally with
respect to the two groups, but the published evidence really doesn't clarify
just what that is. Although I suspect that there are two good biological
species involved, on current evidence it is not clear where the geographical
boundaries are, nor even what the true vocal differences are."

Comments from Jaramillo: "YES - I will be the contrary vote on
this one, perhaps because magellanicus is a bird I have a lot of
experience with throughout Chile, and to me it seems much more distinct vocally
and morphologically from virginianus than many Glaucidium taxa.
Size is not the only distinction from virginianus; it also has rather
small talons, sort of like the difference between Whiskered and Western
Screech-Owls. The voice of magellanicus is absolutely always the same in
Chile, from Tierra del Fuego to the border with Peru, and is consistently
different from that of virginianus. Perhaps they hybridize in northern
Peru with nigrescens, perhaps they do not, and a bit of hanky-panky
between related species is not unheard of, so that does not trouble me. I do
think it is worth figuring out what nigrescens is, and what is
going on there though. In northern Argentina, the lowland birds are vocally
indistinguishable to my ears from North American virginianus. So we have
these two vocal groups that are found over vast areas of the American
continent, they seem to show little or no geographic variation, and they appear
to be parapatric in at least one area (Salta, Argentina) with one being a
lowland form, the other a highland form. This is the classic pattern of two
good biological species. Granted that there may be something more complex going
on in northern Peru that does not invalidate the big picture. This is
independent of any dubious genetic work done by Kšnig.

"Some
additional notes on magellanicus. In southernmost Chile this owl
seems to show a distinct preference for Tuco-tucos (Ctenomys). It is
also fond of nesting on the ground, and it is common to find it relatively
active during the day. I have played virginianus tape to birds in Chile
just out of curiosity and they completely ignore the tape. Farther north the
species is much less common, particularly in the central zone as it shuns
forest. In the far north it is found in various open areas, often near cliffs
for nesting, including desert valleys and ravines within the lower Puna. I
should ask Dan Lane what the habitats are like in this possible area of
intergradation."

Comments from Cadena: "NO. Alvaro's points are well-taken, but
we should wait until the relevant data have been analyzed in detail and
presented in a publication."